The electrical excitability of nerve, muscle, heart, and other cells depends on ion channels. Mutations of ion channels cause a number of inherited diseases. Understanding how ion channels are regulated is an important basic and clinical science goal. We propose to use the communication signals of a weakly electric fish as a model system to elucidate how ion currents are regulated. The electric organ discharge (EOD) is a sexually dimorphic, hormone-sensitive, and individually distinct communication signal. The wave shape of the EOD is intimately dependent on and reflective of the membrane properties of the cells in the electric organ because these signals are in the currency of the nervous system--electricity. We have shown that the wave shape of the EOD pulse is determined by Na+ and K+ currents and that the biophysical properties of these currents are sexually dimorphic, individually distinct, and hormonally modulated. In the last granting period we cloned three K+ channel genes from the electric organ and observed that two of them are expressed in high levels in females and low levels in males, and that their levels are suppressed by androgens. The third is expressed similarly in both sexes and is unaffected by hormones. We also discovered a unique Na+ channel gene. In this proposal we continue to focus on the molecular regulation of the K+ and Na+ currents. Specific aim 1 is to study how the three K+ channel genes generate the observed variation in K+ current kinetics using subunit-specific channel blocking peptides, Western blotting and immunoprecipitaiton, and acolyte injection. Specific aim 2 is to clone and the study the expression and 3ossible hormone regulation of one or more additional candidate K+ channel genes. Specific aim 3 is to: lone and test the possible role of K+ channel beta subunits in regulation of K+ current properties. Specific aim 4 is to study differential expression and hormonal regulation of two splice forms of a Na+ channel beta subunit, and how the different splice forms might influence the inactivation rate of the Na+ current. [unreadable] [unreadable] [unreadable]